Movement of air in the atmosphere from areas of high pressure to areas of low pressure is a source of clean, sustainable energy for meeting a portion of the world's growing energy needs. Commercial utilization of wind energy has steadily increased over the past few decades, but is well shy of providing a significant percentage of global electrical power demand. Ground-based wind turbines have grown in size from the 100 kilowatt class to the multi-megawatt class. However, the amortized cost per kilowatt-hour for terrestrial wind turbines has recently stagnated. New, larger wind turbines require extremely large cranes for tower, nacelle, and blade installation. The rotor blades must be transported in sections on long flat bed trucks.
Modern large terrestrial wind turbines utilize either extremely heavy step-up gearboxes that have input torques in the millions of pound-feet and drive one or more generators at moderate speed, or do not utilize a gearbox and directly drive an extremely large and heavy generator at low speed. Gearbox reliability is low, and maintenance costs are high. These factors have set a cannot-be-lower-than value for the cost per kilowatt-hour for terrestrial wind power systems.
Therefore, it would be desirable to provide an effective wind turbine energy conversion device that is relatively inexpensive to manufacture, deploy, and maintain. It would also be desirable for the device to be able to be utilized in locations that are impractical for ground-based wind turbines.